Perpendicular standing spin waves (PSSWs) have been intensively studied to realize high frequency magnetic oscillations with low bias field. Our previous work reported larger than 20 GHz PSSW with only 100 Oe bias field in the undulating CoFeB thin film. In this work, a finite difference model was developed to simulate the time evolvement of magnetization by solving Landau–Lifshitz–Gilbert equation. In the model, the magnetization oscillation was studied with an applied AC magnetic field to the film. Simulation results show good agreement with the PSSW predicted resonance frequency vs. bias field as compared to experimental data. Furthermore, the PSSW is caused by the non-uniform magnetization through the thickness. The results also suggest the appropriate trend between the pumping current (proportional to the magnetization oscillation energy) and the bias field. Based on this model, we used both gradient descent and parametric sweep methods to optimize the geometry of the undulating structure. The resultant optimized design can achieve more than twice the spin pumping current compared to the pre-optimized design. This provides a better understanding of the design methodology necessary for high-frequency spintronic applications.